Neutron detection

Abstract

A neutron detector includes a microchannel plate having a structure that defines a plurality of microchannels, and layers of materials disposed on walls of the microchannels. The layers include a layer of neutron sensitive material, a layer of semiconducting material, and a layer of electron emissive material. For example, the layer of neutron sensitive material can include boron-10, lithium-6, or gadolinium.

What is claimed is: 
     
       1. An apparatus comprising:
 a microfiber plate comprising:
 a plurality of microfibers that define interstices between the microfibers; 
 layers of materials disposed on surfaces of the microfibers, the layers including a layer of neutron sensitive material, a layer of semiconducting material, and a layer of electron emissive material, in which the layer of semiconducting material does not include neutron sensitive material; 
 an input electrode; and 
 an output electrode, in which the microfibers are disposed between the input and output electrodes. 
 
 
     
     
       2. The apparatus of  claim 1  in which the layer of neutron sensitive material comprises at least 50 mol % of neutron sensitive material. 
     
     
       3. The apparatus of  claim 1  in which the layer of neutron sensitive material comprises at least one of boron-10, lithium-6, or gadolinium. 
     
     
       4. The apparatus of  claim 1  in which the layer of neutron sensitive material comprises a compound that comprises at least one of boron-10, lithium-6, or gadolinium, and the compound comprises at least one of boron-10 oxide, boron-10 nitride, lithium-6 oxide, or gadolinium oxide. 
     
     
       5. The apparatus of  claim 1  in which the layer of neutron sensitive material has a thickness in a range from 0.5 to 5 microns. 
     
     
       6. The apparatus of  claim 1  in which the layer of semiconducting material has a thickness in a range from 50 to 1000 nm. 
     
     
       7. The apparatus of  claim 1  in which the semiconducting material comprises AlZn x O y  alloy, x and y being positive integers. 
     
     
       8. The apparatus of  claim 1 , comprising a data processor to determine whether a neutron has been detected based on information derived from a charge induced on the output electrode. 
     
     
       9. A method of fabricating a microfiber plate, the method comprising:
 providing a plurality of microfibers that define interstices between the microfibers; and 
 depositing layers of materials on surfaces of the microfibers, including
 depositing a layer of neutron sensitive material, 
 depositing a layer of semiconducting material, and 
 depositing a layer of electron emissive material. 
 
 
     
     
       10. The method of  claim 9  in which depositing a layer of neutron sensitive material comprises using atomic layer deposition to deposit a layer of neutron sensitive material. 
     
     
       11. The method of  claim 10  in which using atomic layer deposition to deposit a layer of neutron sensitive material comprises using atomic layer deposition to deposit a layer of a material comprising at least one of boron-10, gadolinium, or lithium-6. 
     
     
       12. The method of  claim 10  in which using atomic layer deposition to deposit a layer of neutron sensitive material comprises using atomic layer deposition to deposit a layer of compound material comprising at least one of boron-10, gadolinium, or lithium-6, and the compound material comprises at least one of boron-10 oxide, boron-10 nitride, lithium-6 oxide, or gadolinium oxide. 
     
     
       13. The method of  claim 10  in which using atomic layer deposition to deposit a layer of neutron sensitive material comprises using atomic layer deposition to deposit at least two of boron-10, lithium-6, or gadolinium. 
     
     
       14. The method of  claim 9  in which depositing a layer of semiconducting material comprises using atomic layer deposition to deposit a layer of semiconducting material. 
     
     
       15. The method of  claim 9  in which depositing a layer of electron emissive material comprises using atomic layer deposition to deposit a layer of electron emissive material. 
     
     
       16. The method of  claim 9  in which depositing a layer of neutron sensitive material, a layer of semiconducting material, and a layer of electron emissive material on the microfibers comprises depositing a layer of neutron sensitive material, followed by depositing a layer of semiconducting material, and followed by depositing a layer of electron emissive material on the microfibers. 
     
     
       17. A method of detecting neutrons, the method comprising:
 using a layer of neutron sensitive material formed on surfaces of microfibers of a microfiber plate to capture a neutron and generate at least one reactant particle; 
 detecting secondary electrons that are generated based on an interaction between the reactant particle and a layer of electron emissive material on the surfaces of the microfibers; 
 flowing a bias current through a layer of a semiconducting material formed on a surface of each of at least some of the microfibers to neutralize positive surface charges due to emission of secondary electrons, the layer of the semiconducting material not containing the neutron sensitive material; and 
 generating a first signal indicating detection of a neutron. 
 
     
     
       18. The method of  claim 17 , further comprising generating a second signal indicating detection of the secondary electrons, generating a third signal indicating detection of a gamma ray, determining whether the third signal occurred within a specified time period after occurrence of the second signal, and generating the first signal only if the third signal occurred within the specified time period after occurrence of the second signal. 
     
     
       19. The method of  claim 17 , comprising determining whether a neutron has been detected based on information derived from a charge induced on an output electrode of the microfiber plate. 
     
     
       20. The method of  claim 17 , comprising determining whether a neutron has been detected based on first information derived from a first charge induced on an input electrode of the microfiber plate and second information derived from a second charge induced on the output electrode of the microfiber plate.